Inhalation exposure to carbon monoxide represents a major cause of environmental poisoning. Individuals can be exposed to carbon monoxide in the air under a variety of circumstances, such as house fires, use of generators or outdoor barbeque grills used inside the house, or during suicide attempts by running automobiles in closed spaces. Carbon monoxide binds to hemoglobin and to hemoproteins in cells, in particular, the enzymes of the respiratory transport chain. The accumulation of carbon monoxide bound to hemoglobin and other hemoproteins impairs oxygen delivery and oxygen utilization for oxidative phosphorylation. This ultimately results in severe hypoxic and ischemic injury to vital organs such as the brain and the heart. Individuals who accumulate greater than 15% carbon carboxyhemoglobin in their blood are at risk for brain injury and neurocognitive dysfunction. Individuals with higher levels of carboxyhemoglobin are at risk for death. Patients with very high carboxyhemoglobin levels typically suffer from irreversible brain injury and brain death.
Despite the availability of methods to rapidly diagnose carbon monoxide poisoning with standard arterial and venous blood gas analysis and co-oximetry, and despite an awareness of risk factors for carbon monoxide poisoning, there are no available antidotes for this toxic exposure. The current therapy is to give 100% oxygen by face mask, and when possible to expose patients to hyperbaric oxygen. The mechanism for hyperbaric oxygen therapy is the oxygen will increase the rate of release of the carbon monoxide from hemoglobin and from tissues and accelerate the natural clearance of carbon monoxide. However, this therapy has only a modest effect on carbon monoxide clearance rates and based on the complexity of hyperbaric oxygen facilities, this therapy is not available in the field.